Modern telecommunication systems include heterogeneous mixtures of second, third, and fourth generation (2G, 3G, and 4G) cellular-wireless access technologies, which may be cross-compatible and may operate collectively to provide communication services. Global Systems for Mobile (GSM) is an example of 2G telecommunications technologies; Universal Mobile Telecommunications System (UMTS) is an example of 3G telecommunications technologies; and Long Term Evolution (LTE), including LTE Advanced, and Evolved High-Speed Packet Access (HSPA+) are examples of 4G telecommunications technologies.
A cellular-wireless network (e.g., may also be referred to as mobile telephone network) includes multiple communication cells or “cells”, where an individual cell is associated with an area of coverage. A cell may be served by one or more fixed location transceivers (e.g., transmitter(s) and receiver(s)) equipped in a base station. The fixed location transceivers and the base station, along with other equipment and components, may collectively be referred to as a cell site.
Recently, cellular-wireless access technologies, particularly 4G telecommunications technologies (e.g., LTE, LTE Advanced, etc.), have begun to implement multiple-input and multiple-output (MIMO), which uses multiple antennas to exploit multipath propagation and to increase data throughput (e.g., down-link data throughput). For instance, an individual cell site may implement a “4×2” MIMO implementation in which four (4) transmitting antennas are used to transmit information to mobile devices (e.g., data pushed to a mobile device or data requested by a mobile device) and two (2) receiving antennas are used to receive information from mobile devices.
However, cellular-wireless access technologies that implement MIMO often experience interference that causes system level performance degradation in a mobile telephone network. More specifically, control channel interference occurs when the transmissions of first reference signals from the transmitting antennas of a first cell site interfere with the transmissions of second reference signals from the transmitting antennas of a second cell site that neighbors the first cell site. The interference occurs because the neighboring cell sites often use the same frequency bands and because the coverage areas of the neighboring cell sites often overlap.